Ion Selective Membrane Electrodes for Stability-Indicating Determination of Amisulpride

This work describes the construction and electrochemical response characteristics for three different polyvinyl chloride (PVC) membrane sensors for determination of amisulpride in presence of its degradation products and commonly used excipients. The first two sensors are based on the ion association complexes of amisulpride cation with sodium tetraphenyl borate (TPB) [sensor 1] or ammonium reineckate (R) [sensor 2] counter anions as ion exchange sites in PVC matrix. β-cyclodextrin (β-CD)-based technique with TPB as a fixed anionic site in PVC matrix was used for fabrication of the third membrane sensor [sensor 3]. The performance characteristics, sensitivity and selectivity of these electrodes in presence of amisulpride degradation products were evaluated according to IUPAC recommendations. Fast, stable and linear response was obtained for amisulpride over the concentration range 1×10-6-1×10-2 M for sensors 1 and 3 while for sensor 2 it was found to be 1×10-5-1×10-2 M. The proposed sensors showed stable Nernstian responses of 29.1, 28.2 and 31.1 mV per concentration decade with sensors 1, 2 and 3, respectively. These sensors exhibit fast response time (10-20 s) and good stability (4-6 weeks). The direct potentiometric determination of amisulpride in its pure form using the proposed sensors gave average recoveries of 99.93±0.72, 100.01±0.93 and 99.94±0.87 for sensors 1, 2 and 3, respectively. The sensors were used for determination of amisulpride, in pure form, in presence of its degradation products, in tablets and in plasma. Validation of the method shows suitability of the proposed sensors for use in the quality control assessment of amisulpride and for routine analysis as stability indicating method. The developed method was found to be simple, accurate and precise when compared with a reported RP-HPLC method.